问题补充:
--- have you studied in this school?
--- For about two years.
A. How often
B. How long
C. How much
D. How many
答案:
A. How often
(答案→)B. How long
C. How much
D. How many
解析:How often多久一次;How long多长;How much多少钱;How many多少个。根据下文,大约两年。可知上文提问的是时间长短,故选B。